The invention relates to an actuating drive that is intended to adjust a plurality of actuators in a nuclear resonance spectrometer. Actuating drives of this kind can be present especially in an NMR sample head for acquiring the nuclear resonance spectra of various nuclear species, and are used therein to tune the frequency and set the impedance matching. For this purpose there are provided in known sample heads, for example in order to set the value of a capacitor for frequency tuning, four slide rods which, depending on their slide position, activate capacitors with different values. The value of the effective capacitance can generally be read from a scale on the rods using the decimal system. A sample head can additionally or exclusively have rotating actuators for tuning and matching. A change in tuning and/or impedance matching is necessary, for example, when the nuclear signal of another nuclear species is to be acquired, when the sample is changed, or when changes in temperature occur.
Processes with which frequencies can be set and impedances matched relatively quickly are known. In one process disclosed by DE-A1-38 38 252, for example, the sample head and a reference impedance are alternately connected to a preamplifier attached to the sample head; by comparing the reading obtained therewith, the discrepancy between the instantaneous complex impedance of the sample head and the reference status indicated by the reference impedance is determined, and the user is thereby informed as to how the tuning and matching elements must be adjusted. Because the device from which the specific mismatch and discrepancy in natural frequency of the sample head can be read is located at a distance from the sample head-specifically, on the operating console of the nuclear resonance spectrometer, while the sample head is located inside the magnet of the nuclear resonance spectrometer-the adjustment process itself is awkward and time-consuming, since the user must often move back and forth between the operating console and sample head. To set the frequency and/or matching, it may also be necessary to manipulate actuators elsewhere on a nuclear resonance spectrometer, for example if settable electrical filter circuits need to be tuned.